CN109290629B

CN109290629B - Oscillating tool machine

Info

Publication number: CN109290629B
Application number: CN201810819233.2A
Authority: CN
Inventors: A.黑斯; F.贝克
Original assignee: C & E Overtone Co ltd
Current assignee: C & E Overtone Co ltd
Priority date: 2017-07-25
Filing date: 2018-07-24
Publication date: 2020-09-01
Anticipated expiration: 2038-07-24
Also published as: CN109290629A; US11207738B2; EP3434432B1; EP3434432A1; US20190030616A1; DE102017116823A1

Abstract

An oscillatory-driven machine tool is specified, comprising a housing (12), in which a motor (26) having a motor shaft (28) is accommodated, at which an eccentric element (30) is accommodated, a spindle head (20), a tool spindle (22) which is mounted in the spindle head (20) so as to be rotatable about its longitudinal axis, a coupling element (46) being accommodated in a rotationally fixed manner at the tool spindle, the coupling element interacting with the eccentric element (30) in order to generate an oscillatory movement of the tool spindle (22) about its longitudinal axis (23) in such a way that, in addition to the oscillatory movement, superimposed movements which differ from the oscillatory movement are introduced into the coupling element (46).

Description

Oscillating tool machine

Technical Field

The invention relates to an oscillatingly (oszillierend) driven machine tool having a housing in which a motor with a motor shaft is accommodated, at which an eccentric element is accommodated, having a tool spindle rotatably mounted in the housing about its longitudinal axis, a coupling element being accommodated in a rotationally fixed manner at the tool spindle, which coupling element interacts with the eccentric element for producing an oscillatory movement of the tool spindle about its longitudinal axis.

Background

Such an oscillatingly driven tool machine (also referred to herein simply as an oscillatory drive) typically converts an eccentric movement of an eccentric element driven by the motor spindle into a rotary oscillatory movement of a coupling element fixedly connected to the motor shaft, which coupling element is in most cases configured as a fork, which encompasses a spherical bearing in which the eccentric element is accommodated.

Such oscillating drives are usually designed to drive the tool at a high oscillation frequency (for example in the range between 5000 oscillations per minute and 30000 oscillations per minute) with a small oscillation angle (for example in the range between 0.5 ° and 7 ° (measured from the reversal point (Umkehrpunkt) to the reversal point)). This enables high-precision machining of the workpiece.

The tool driven in an oscillating manner generates only a small reaction force or reaction torque which an operator who manipulates the oscillating drive must bear (affangen) when machining a workpiece. For example, in comparison to rotationally driven sawing tools, such as circular saws, an oscillating saw blade represents a significantly lower risk of injury for the user. Furthermore, the use of an elongated saw blade also enables a plunge cut (tauchnitte) to be introduced into workpieces made of wood, GFK, plaster or the like, which is only possible to a limited extent with rotationally driven tools.

EP 2886271 a2 discloses an oscillatingly driven machine tool in which a drive movement of the oscillatingly driven rotary oscillation is additionally superimposed with a movement directed perpendicular to the longitudinal axis of the tool spindle.

Separate drives are provided for producing the superimposed movement, which results in high technical effort.

A further oscillatingly driven machine tool is known from DE 102006022804 a1, in which the tool, in addition to its oscillating movement, oscillates about an oscillation axis which moves back and forth along a movement path. For this purpose, a separate slider crank drive (schubkurbebelantrieb) is provided.

Here, a consumable structure is likewise obtained. In addition, the additional superimposed rocking or oscillating movement is more precisely disadvantageous for the sawing operation.

A further oscillatably drivable tool machine is known from DE 102014119141 a1, in which at least one controllable actuator is provided for adding at least one further movement component to the rotary oscillatory movement of the tool spindle.

The additionally necessary drive, which usually requires a plurality of actuators, likewise results in an expensive and costly construction.

Disclosure of Invention

Against this background, the present invention is based on the object of providing an oscillatingly driven machine tool in which the tool spindle is oscillatingly driven about its longitudinal axis and can additionally superimpose a movement, wherein the construction should be as simple and robust as possible.

The object is achieved by an oscillatingly driven tool machine having a housing in which a motor having a motor shaft is accommodated, at which an eccentric element is accommodated, having a spindle head, having a tool spindle which is mounted in the spindle head so as to be rotatable about its longitudinal axis, wherein a coupling element is accommodated in a rotationally fixed manner at the tool spindle, wherein the coupling element interacts with the eccentric element for generating an oscillatory movement of the tool spindle about its longitudinal axis in such a way that, in addition to the oscillatory movement, a superimposed movement which is different from the oscillatory movement is introduced into the coupling element.

The object of the invention is solved in this way.

According to the invention, the superimposed movement is produced by means of a drive with the eccentric element, without a separate drive being required for this.

Since in this way an additional drive for generating the superimposed movement can be dispensed with, a significantly simplified embodiment is obtained compared to conventional designs.

According to a further embodiment of the invention, the tool spindle is rotatably mounted in the housing, preferably in the region of its two ends, by means of two bearings and is additionally mounted in a rotationally fixed manner in a linearly movable manner relative to the longitudinal axis.

In this way, a movement of the tool spindle perpendicular to its longitudinal axis can be introduced into the coupling element.

According to a further embodiment of the invention, the coupling element is a lever which is fixed to the tool spindle between the two supports.

According to a preferred embodiment of the invention, the coupling element is guided in the guide groove guide by means of a guide element for generating the superimposed movement.

In this way, a movement is imparted (aufgepr ä gt) to the coupling element, which movement is generated by the movement of the guide element in the guide groove guide.

Different movements can be achieved by varying the shape of the guide groove guide.

Different superimposed movements can also be achieved by changing the guide groove guide of a predetermined design on the tool machine that is driven in an oscillating manner.

The guide groove guide is preferably arranged and designed in such a way that it is symmetrical with respect to a line of symmetry which extends between the two reversal points of the coupling element through the longitudinal axis of the tool spindle.

In this way, the additionally applied linear movement has the same amplitude on both sides, starting from the center of the oscillating movement.

Such an embodiment is particularly suitable when the tool machine is used, for example, for driving a sawing tool.

Naturally, in principle, arrangements other than this can also be considered, which are not symmetrical in order to meet certain specific requirements.

Preferably, the guide groove guide is arranged to be replaceable.

In this way, different superimposed movements can be generated.

According to a further embodiment of the invention, a ball-shaped bearing is received on the eccentric element, which bearing is held on its outer side in the fork-shaped coupling element.

In this embodiment, the design of the oscillatory drive itself corresponds to the usual embodiment known from the prior art.

According to a further embodiment of the invention, means are provided for moving the guide element and the guide groove guide between an engagement position, in which the guide element is guided in the guide groove guide for producing a superimposed movement, and an inoperative position, in which the guide element is out of engagement with the guide groove guide and furthermore prevents linear mobility.

In this way, the superimposed movement can be switched on or off.

For this purpose, for example, the guide groove guide can be adjusted by means of a drive, for example by means of a threaded fastener (gewendeschraube), in such a way that the guide element comes out of engagement with the guide groove guide and thus no additional movement is applied to the oscillating movement. In this case, means are also provided for blocking the linear mobility of the tool spindle in the inoperative position of the guide groove guide, so that the tool spindle is driven in this case only rotationally oscillatory manner and can move only rotationally oscillatory manner.

According to a further embodiment of the invention, means are provided for bringing the guide element into engagement with different guide groove guides or with different sections of a guide groove guide for producing different superimposed movements.

Different superimposed movements can thereby be achieved or superimposed movements can be completely avoided.

According to a further embodiment of the invention, the eccentric element is designed as a ball head which is guided in an internal guide groove guide in the coupling element.

In this way, the spherical bearing on the eccentric element and the outer guide groove guide are omitted, and instead the eccentric element is designed as a ball head which is guided directly in the inner guide groove guide in the coupling element.

This results in a particularly simple construction.

Since a movement component in the axial direction is also generated here, it is advantageous here for the motor shaft to be additionally locked (schern) against displacement in the axial direction. It is also expedient for this to hold the front anchoring support (Ankerlager) in both axial directions.

According to a further embodiment of the invention, the tool spindle projects outwardly from the housing and is sealed in the region of its exit from the housing with a diaphragm made of an elastomer material.

In this way, a reliable sealing of the tool spindle outward can be ensured, although the tool spindle performs not only a rotary oscillating movement, but also a movement perpendicular to its longitudinal axis.

According to a further embodiment of the invention, the guide groove guide is designed such that, when the coupling element is in an intermediate position between the two reversal points of the oscillating movement, superimposed linear movements perpendicular to the longitudinal axis of the tool spindle have a maximum offset.

It has been shown that this design is particularly suitable when the tool machine is used for sawing. In this way, a very good working development (arbeitsfortschrit) can be achieved with a minimum feed force.

According to a further embodiment of the invention, the tool spindle has a fixed tool receptacle at its free end for a tool, in particular a sawing or grinding tool.

The tool holder can be any interface between a tool and a tool spindle known in the prior art, which preferably ensures a form-and/or force-fitting fixing of the tool on the tool spindle. In particular, tool receptacles with a three-dimensional design can also be provided, as is known, for example, from german utility model document DE 202013006900U 1, which is hereby fully incorporated by reference.

According to a further embodiment of the invention, a control unit is provided, which is coupled to the motor in such a way that the control of the motor speed is dependent on one or more predetermined parameters.

For example, means can be provided for detecting the rotational speed of the motor, and the control unit is designed for starting the motor at a first rotational speed (anal uf) and for increasing the rotational speed to a second rotational speed which is higher than the first rotational speed when a load on the motor is detected.

In this way, a so-called idle reduction (leerlafabsenkung, sometimes referred to as idle reduction) can be achieved, whereby a cutting start (Schnittansatz) is first produced at the workpiece during the sawing process at a low rotational speed and then the rotational speed is increased without losing control with respect to the profile, since the saw blade is guided in the profile that has already been produced.

In this way a very rapid working progress can be obtained without the risk caused by the running out (Weglaufen) of the tool.

In this case, a second (increased) rotational speed can be preset or, for example, it can be adjusted to a maximum rotational speed depending on a specific tool.

In this case, the control unit can be designed in such a way that, when a drop in the load is detected, the rotational speed of the motor is also reduced, if necessary until the first rotational speed is reached again.

It is understood that the features of the invention mentioned above and yet to be explained below can be used not only in the respectively given combination, but also in other combinations or alone (in Alleinstellung) without leaving the scope of the invention.

Drawings

Further features and advantages of the invention result from the following description of a preferred embodiment with reference to the drawings. Wherein:

fig. 1 shows a perspective overall view of a machine tool according to the invention;

fig. 2 shows a partial section through a part of the machine tool according to fig. 1 through the spindle head and through the motor;

fig. 3 shows a section through the machine tool according to fig. 2 along the line III-III;

fig. 4 shows a partially cut-away (freegeschnittene) perspective representation in which the coupling element can be seen in particular with a spherical bearing guided therein and a guide element according to the guide groove guide;

FIG. 5 shows an enlarged illustration according to FIG. 4, which illustration is further cut away to enable the oscillating drive to be better seen;

fig. 6 shows a view of the coupling element according to fig. 5 with the associated guide groove guide, viewed from the fork-shaped receptacle for the spherical bearing;

fig. 7 shows a representation of the coupling element with the associated guide groove guide, wherein the spherical bearing with the eccentric element accommodated therein can additionally be seen;

fig. 8 shows a representation of an alternative embodiment of the invention, in which the eccentric element is designed at its end as a ball head which is guided in an inner guide groove guide at the end of the coupling element;

fig. 9 shows the coupling element according to fig. 8, however without the eccentric head;

fig. 10 shows an exemplary illustration of a sawing tool which can be fixed on the end of the outer part of the tool spindle;

fig. 11 shows a simplified circuit diagram for elucidating the idle lowering of the motor;

fig. 12 shows a schematic representation in which a symmetrical arrangement of the guide groove guide with respect to a line of symmetry between the two reversal points of the coupling element is shown;

fig. 13 shows a further variant of the machine tool according to the invention, wherein the modified guide groove guide is shown here only in a perspective illustration;

fig. 14 shows a section through a further variant of the machine tool according to the invention in the region of the fork;

fig. 15 shows a perspective view of the associated guide groove guide from above, an

Fig. 16 shows a perspective view of the associated guide groove guide from below.

Detailed Description

Fig. 1 shows a power tool according to the invention in the form of a hand-held power tool (Handwerkzeug), which is designated in its entirety by the numeral 10. The machine tool 10 has an elongated housing 12 which can be gripped by hand and which is provided at its upper side with a switch 16 for switching on and off.

At the front end of the housing 12, a spindle head 20 is molded, from which a tool spindle 22 projects downward with a free end. At the rear end facing away from the spindle head 20, a replaceable battery pack 14 for the voltage supply of the machine is provided. It is understood that it is naturally possible to use a grid-connected (netzgebunden) embodiment instead of the battery pack.

At the left side, an adjusting wheel 18 can additionally also be seen, which is designed to adjust the maximum rotational speed of the drive motor.

A more detailed construction of the machine tool 10 will now be described in accordance with the following figures.

Fig. 2 shows a longitudinal section through the outer end of the machine 10.

A motor 26 is accommodated in the housing 12, and on its motor shaft 28, an eccentric element in the form of an eccentric pin is fixed by press-fitting at an outer end 33 with a hollow cylindrical projection 32 molded thereon. The motor shaft 28 is supported in the ball bearing by the outer periphery of the projection 32.

The tool spindle 22 is held in the spindle head 20 with its longitudinal axis 23 perpendicular to the longitudinal axis 29 of the motor shaft. The tool spindle is rotatably mounted in the region of its two ends by means of two bearings 34, 36. Additionally, the tool spindle 22 is mounted so as to be movable in a direction perpendicular to its longitudinal axis 23 and parallel to the longitudinal axis 29 of the motor shaft 28. For this purpose, a bearing 34 is held at the inner end of the tool spindle 22 in a bearing mount 38 which is mounted by means of two axial needle bearings (axialnaldelager) 41, 42 and two linear guides (not shown) and can be displaced in a direction parallel to the longitudinal axis 29 of the motor shaft 28. In a corresponding manner, a further bearing, embodied as a needle bearing 36, is held in a bearing support 40, which bearing support 40 is supported by means of two

axial needle bearings

43, 44 and two linear guides (not shown) and can be moved in a direction perpendicular to the longitudinal axis 23 of the tool spindle and parallel to the longitudinal axis 29 of the motor shaft 28.

The tool spindle 22 is thereby driven in a rotationally oscillating manner about its longitudinal axis 23 (see double arrow 25) and additionally moves in a direction perpendicular to its longitudinal axis 23 and parallel to the longitudinal axis 29 of the motor shaft 28 (see double arrow 27).

In order to produce a rotationally oscillating and superimposed linear movement, a coupling element 46 in the form of a lever is held at the end on the tool spindle 22 in a rotationally fixed manner between the two supports 34, 36 by means of a press fit.

The coupling element 46 (the shape of which can be seen in particular in more detail in fig. 4 and 5) has a cylindrical opening 54 (fig. 4, 5) at one end, which allows a connection with the tool spindle 22 by means of a press fit. The opposite second end is embodied in the form of a fork 56. At one side (lower side) of the fork, the fork 56 is downwardly elongated and has a U-shaped cross-section according to fig. 3. A spherical bearing 48 is held on the eccentric 33 and is received in a mating surface (Sitzfl ä che) 60 on the inside of the fork 56.

Below the fork 56, a block 51 with a guide groove guide 52 is held at the housing 12, into which a guide element 50 in the form of a pin engages, which projects downwards from the lower end of the fork 56.

If the eccentric 33 is driven by the motor shaft 28, a rotationally oscillating movement of the tool spindle 22 about its longitudinal axis 23 is generated via the spherical bearing 48 and the coupling element 46 (see double arrow 25). On the other hand, a superimposed oscillating linear movement (double arrow 27) is generated by engaging the guide element 50, which is fixedly connected to the fork 56, into the guide groove guide 52, on the tool spindle 22, i.e. a superimposed oscillating linear movement perpendicular to its longitudinal axis 23 and parallel to the longitudinal axis 29 of the motor shaft 28.

The course of the superimposed oscillating linear movement can be influenced by the arrangement and shape of the guide groove guide 52.

According to a preferred embodiment of the invention, the guide groove guide 52 is arranged and designed in such a way that it is symmetrical with respect to a line of symmetry 76 which extends between the two

reversal points

74, 75 of the coupling element 46 through the longitudinal axis 23 of the tool spindle 22 (see fig. 12). In fig. 12, the angle between these two reversal points (which is between 0.5 ° and 7 °) is clearly shown too high for better visibility.

In this case, the linear movement produced by the guide groove guide 52 has the same stroke on both sides at the same distance from the respective reversal points 74, 75 of the oscillating movement.

This embodiment is advantageous when the tool machine is to be used for driving a sawing tool.

For this purpose, the guide groove guide 52 is preferably designed such that, when the coupling element 46 is in the intermediate position between its two

reversal points

74, 75, the superimposed linear movements perpendicular to the longitudinal axis 23 of the tool spindle 22 have a maximum offset.

It has been shown that this design is particularly suitable for producing very good work progress with a minimum feed force during the sawing operation.

In fig. 10, an exemplary tool 64 is shown in a top view, which can be used as a sawing tool. The tool has a cutting portion 68 provided with saw teeth, which extends concentrically to a fastening opening 66 for fastening the tool 64 to the tool holder 24 on the outer end of the tool spindle 22.

It is understood that the shape of the fastening opening 66 (which is shown here as a polygon by way of example only) is adapted to the shape of the associated receptacle 24 on the tool spindle 22. In the embodiment shown, for fastening the tool 64, fastening elements are additionally used, which act (greift) through fastening openings 66 of the tool 64 and are fastened in the tool spindle in order to ensure a form-and/or force-fitting connection. However, since the details of this fixing are known, a more detailed presentation is abandoned in this connection.

As is indicated in fig. 5 by way of example by the double arrow 58, it is possible for the guide groove guide 52 to be displaced, for example by a movement of the block 51 (in which the guide groove guide 52 is formed), between the engagement position shown in fig. 5, in which the guide element 50 engages in the guide groove guide 52, and an inoperative position.

In the inoperative position, the block 51 is moved away from the guide element 50 so far that the guide element 50 no longer engages in the guide groove guide 52. In this position, only a rotary oscillating movement, but not an additional linear movement, is transmitted to the tool spindle 22.

This movement can be produced, for example, by replacing the fixed threaded fastener 59, which can be seen in fig. 5, by a threaded spindle which engages with a thread in the block 51 and thus allows an adjustment in the direction of the double arrow 58. In this case, means (not shown) are furthermore provided for blocking the linear mobility of the tool spindle in the inoperative position of the guide groove guide, so that the tool spindle is driven in this case only in a rotationally oscillating manner and can move only in a rotationally oscillating manner.

Fig. 8 and 9 show a variant embodiment of the invention in which, instead of a guide groove guide 52 interacting with the guide element 50, a connection is provided directly between the eccentric and the coupling element in the region of the fork.

In this case, the eccentric 30a is designed at its outer end as a ball head which engages in an inner guide groove 62 at the end of the coupling element 46a in the region of the fork 56a (see fig. 9). The movement is fixedly preset by the form of the inner guide groove guide 62 in conjunction with the ball head portion 30a of the eccentric. The movement curves can be adapted by the design of the inner guide groove guide 52.

As can be seen from fig. 2, the tool spindle 22 is sealed at its outer end by a diaphragm 53 made of an elastomer material, since the tool spindle 22 additionally moves linearly in an oscillating manner.

In order to support the execution of the sawing operation, the machine tool 10 is preferably additionally designed with a so-called idle descent.

A central control unit 70 (which is schematically illustrated in fig. 11 and interacts with motor 26) is designed in such a way that tool 64 is rotated at a low speed n when the sawing cut begins₁This enables the tool 64 to be handled very well. If the controller 70 coupled to the motor 26 recognizes that the motor 26 is loaded, the rotational speed is slowly increased to a higher rotational speed n₂If necessary, until a preset maximum rotational speed is reached.

A very rapid working progress can thereby be obtained without losing control over the profile, since the saw blade is guided in the profile already produced. If it is notThe load on the machine is reduced again, and the rotational speed is reduced again until finally the lower level n is reached again₁。

In fig. 13, a further variant of the machine tool according to the invention is indicated overall by 10 b. Only the block 51b is shown with the guide groove guide 52b with the central region 74 and the first end region 76 and the second end region 78. The block 51b can be displaced in the direction of its longitudinal extension, as indicated by the double arrow 79.

As a result, either the central region 74 or one of the two

end regions

76, 78 can be brought into engagement with the associated guide element 50, in order to thereby produce different superimposed movements. The central region 74 can likewise be used to produce a completely non-superimposed movement, if desired.

Fig. 14 to 16 show a further variant of the machine tool according to the invention, which is generally designated by 10 c. As can be seen from the section according to fig. 14, in the lower end of the fork 56c, a guide element 50c in the form of a tappet remains axially displaceable against the force of a spring element 80. The guide element 50c can be brought into engagement either with the upper guide groove 82 or with a lower guide groove 84 provided at the underside of the block 51 c. Thus, different superimposed movements are obtained depending on whether the upper guide groove 82 or the lower guide groove 84 is in engagement.

Claims

1. An oscillatory-driven machine tool is provided,

having a housing (12) in which a motor (26) having a motor shaft (28) is accommodated, at which an eccentric element (30, 30 a) is accommodated,

comprises a main shaft head (20),

having a tool spindle (22) which is mounted in the spindle head (20) so as to be rotatable about its longitudinal axis (23), a coupling element (46, 46 a) being accommodated in a rotationally fixed manner on the tool spindle, which coupling element interacts with the eccentric element (30, 30 a) in order to generate an oscillating movement of the tool spindle (22) about its longitudinal axis (23) in such a way that, in addition to the oscillating movement, a superimposed movement which is different from the oscillating movement is introduced into the coupling element (46, 46 a), which superimposed movement is generated by a drive using the eccentric element, and the tool spindle being mounted in the housing in the region of the two ends of the tool spindle so as to be rotatable by means of two bearings and additionally mounted so as to be linearly movable in a rotationally fixed manner relative to the longitudinal axis,

wherein the coupling element (46) is guided in a guide groove guide (52, 52b, 82, 84) for producing the superimposed movement by means of a guide element (50, 50 c), or wherein the eccentric element is designed as a ball head (30 a) which is guided in an inner guide groove guide (62) in the coupling element (46 a).

2. The machine tool according to claim 1, wherein the tool spindle (22) is rotatably mounted in the housing (12) by means of two bearings (34, 36) and is additionally mounted so as to be linearly movable perpendicular to the longitudinal axis (23).

3. The machine tool according to claim 2, wherein the coupling element (46, 46 a) is a lever which is fixed on the tool spindle (22) between the two supports (34, 36).

4. The machine tool according to claim 1, wherein the guide groove guides (52, 82, 84) are arranged and configured such that they are symmetrical with respect to a line of symmetry (76) extending between the two reversal points (74, 75) of the coupling element (46) through the longitudinal axis (23) of the tool spindle (22).

5. The machine tool according to claim 1, wherein the guide groove guide (52) is arranged exchangeably.

6. The machine tool according to one of claims 1 to 5, wherein a spherical bearing (48) is accommodated on the eccentric element (30), said bearing being held at its outer side in a fork-shaped coupling element (46).

7. Tool machine according to claim 1, wherein means (59) are provided for moving the guide element (50) and the channel guide (52) between an engaged position, in which the guide element (50) is guided in the channel guide (52) for producing the superimposed movement, and an inoperative position, in which the guide element (50) is out of engagement with the channel guide (52) and furthermore prevents linear movability.

8. The machine tool according to claim 1, wherein means (80) are provided for bringing the guide elements (50, 50 c) into engagement with different guide groove guides (82, 84) or with different sections (78) of the guide groove guide (52 b) for producing different superimposed movements.

9. A machine tool according to claim 7 or 8, wherein the channel guide (52 b) is displaceable along its extension direction.

10. The machine tool of any one of claims 1 to 5, wherein the tool spindle (22) is stopped against displacement in the axial direction.

11. The machine tool according to any one of claims 1 to 5, wherein the tool spindle (22) projects outwardly from the housing (12) and is sealed with a membrane (53) made of an elastomer material in the region of its exit from the housing.

12. The machine tool according to claim 1, wherein the guide groove guide (52, 52b, 62, 82, 84) is designed in such a way that, when the coupling element (46, 46 a) is in an intermediate position between two reversal points (74, 75) of the oscillating movement, superimposed linear movements perpendicular to the longitudinal axis (23) of the tool spindle (22) have a maximum offset.

13. The machine tool according to one of claims 1 to 5, wherein the tool spindle (22) has a fixed tool receptacle (24) for a tool (64) at its free end.

14. A machine tool according to any one of claims 1 to 5, wherein a controller (70) is provided, which is coupled to the motor (26) in such a way that the control of the motor rotational speed (n) is effected in dependence on one or more predetermined parameters.

15. The machine tool of claim 14, wherein means (72) are provided for detecting a rotational speed (n) of the motor (26), and the controller (70) is configured for causing the motor (26) to rotate at a first rotational speed (n)₁) Is started and is used to increase the rotational speed above the first rotational speed (n) when a load of the motor (26) is detected₁) Second rotational speed (n)₂) The above.

16. The machine tool of claim 15, wherein the controller (70) is configured for decreasing the rotational speed (n) of the motor (26) when a decrease in the load is identified.

17. The machine tool according to claim 2, wherein the tool spindle (22) is rotatably supported in the housing (12) in the region of its two ends by means of the two bearings (34, 36) and is additionally supported linearly movably perpendicular to the longitudinal axis (23).

18. The machine tool of claim 13, wherein the tool (64) is a sawing or grinding tool.